Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Before Tax:
Net other comprehensive income (loss)		$ 2		$ 12		$ 10	$ 40
Tax Effect:
Net other comprehensive income (loss)		5		(13)		(4)	(27)
Net of Tax:
Net other comprehensive income (loss)		7	$ (1)	(1)	$ 14	6	13
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		6		(23)		(2)	(28)
Reclassification to earnings		0		0		0	0
Net other comprehensive income (loss)		6		(23)		(2)	(28)
Tax Effect:
Net gain (loss)		5		(4)		(1)	(11)
Reclassification to earnings		0		0		0	0
Net other comprehensive income (loss)		5		(4)		(1)	(11)
Net of Tax:
Net gain (loss)		11		(27)		(3)	(39)
Reclassification to earnings		0		0		0	0
Net other comprehensive income (loss)		11		(27)		(3)	(39)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Before Tax:
Net gain (loss)		(2)		30		13	57
Reclassification to earnings	[1]	(6)		0		(10)	2
Net other comprehensive income (loss)		(8)		30		3	59
Tax Effect:
Net gain (loss)		0		(8)		(3)	(14)
Reclassification to earnings	[1]	1		0		2	0
Net other comprehensive income (loss)		1		(8)		(1)	(14)
Net of Tax:
Net gain (loss)		(2)		22		10	43
Reclassification to earnings	[1]	(5)		0		(8)	2
Net other comprehensive income (loss)		(7)		22		2	45
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before Tax:
Net gain (loss)		0		0		0	0
Reclassification to earnings	[2]	4		5		9	9
Net other comprehensive income (loss)		4		5		9	9
Tax Effect:
Net gain (loss)		0		0		0	0
Reclassification to earnings	[2]	(1)		(1)		(2)	(2)
Net other comprehensive income (loss)		(1)		(1)		(2)	(2)
Net of Tax:
Net gain (loss)		0		0		0	0
Reclassification to earnings	[2]	3		4		7	7
Net other comprehensive income (loss)		$ 3		$ 4		$ 7	$ 7

[1] Pre-tax amount is classified as sales in the accompanying condensed consolidated statements of operations.

[2] Pre-tax amount is classified as non-operating postretirement expense in the accompanying condensed consolidated statements of operations.